Crankcase Ventilation System Description: Operation
WARNING: This page is about a different car, the 2002 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
The primary control is through the crankcase ventilation valve (1) which meters the flow at a rate depending on inlet vacuum. To maintain idle quality, the crankcase ventilation valve restricts the flow when inlet vacuum is high. If abnormal operating conditions arise, the system is designed to allow excessive amounts of blow-by gases to back flow through the crankcase vent into the throttle body to be consumed by normal combustion.